The invention relates to a long-range optical device. A long-range optical device may, in the context of the present invention, be a monocular or binocular telescope, in particular binoculars.
During the use of a long-range optical device, for example binoculars, perturbing movements of the housing of the long-range optical device have a detrimental effect on the image quality of the image seen by the user. The perturbing movements acting on the housing lead to shaking of the image, which compromises the observation of an object or scenery.
Long-range optical devices have therefore been proposed in which the at least one optical channel contains at least one optical element which is movable relative to the housing, as well as a stabilization system for the at least one movable optical element for image stabilization in the event of perturbing movements. By virtue of the relative movability of the at least one optical element in the beam path of the optical channel, this optical element, and therefore the imaging, is decoupled in terms of movement from the housing. Despite perturbing movements, therefore, the user perceives an image which is free of shaking, or has little shaking.
In the long-range optical device known from the document DE 38 43 776 A1, the at least one movable optical element is the image inverting prism, which is gimbal supported in the housing by means of a torsion spring joint. The stabilization system of this known long-range optical device comprises an eddy current damper for damping movements of the inverting prism. The eddy current damper generates a restoring force proportional to the displacement velocity of the image inverting prism during displacement of the image inverting prism. The eddy current damper prevents the image inverting prism from being excited in forced oscillations in the housing.
The eddy current damper of this known long-range optical device comprises a magnet system moved with the image inverting prism, which is formed by permanent magnets, and a plane-parallel plate made of an electrically conductive material, for example copper. The eddy current carrier formed as a plate has a constant cross section and has indentations in the edge region, so that axis-wise adjustment of the damping constant is possible, particularly while taking into account different spring constants of the torsion spring articulation and the inertial mass of the movable components. The eddy current carrier, formed as a plate, is connected firmly to the housing.
An eddy current damper as a damping device of the stabilization system has the advantage that initial friction is minimal, which is not the case for example in a damping device which is based on the principle of damping by fluid friction. Long-range optical devices comprising image stabilization units which are based on damping by the fluid friction are known from DE 2 152 085 A and DE 2 353 101 A.
U.S. Pat. No. 2,688,456 and U.S. Pat. No. 2,829,557 describe damping devices, which consist of two magnet systems, in long-range optical devices. A bar magnet fastened on the stabilization system is arranged in a magnetic cylinder fixed to the housing. In this case, the mutual repulsion forces cause damping of the movement of the at least one movable optical element.